The Hirasawa household is home to a pair of forever-absent parents (it is never too late for another honeymoon; long live youth!) and an older sister with the destructive potential of a demolition squad. But there's also Ui, so they will survive.

Ui mostly concerns herself with her school duties and keeping both her home and sister presentable and in one piece. The latter task, seemingly mundane, in fact requires heroic fortitude and a vast array of skills. Ui is, of course, proficient at cooking, cleaning and decorating the house. She never forgets to wake her sister up for school. She carries a hairbrush in her bag, knowing her sister will often forget to brush her hair in the morning rush. She buys fruit rich in vitamin C when the flu season comes. She... well, you get the point.

Ui is not only hard-working, but also exceptionally talented. When the need arises, she becomes a song lyrics writer overnight. She also learns the guitar in record time and takes her sister's place in a band while in disguise. What eventually gives her away is that she... plays too well.

For all those admirable qualities, Ui is still a normal girl with her own insecurities. It is easy to scare her, for example. She can also act silly sometimes. When her friends come to check up on her fever, she quickly leaps out of bed to prepare tea for them. But that's just simple hospitality, right?